Tested semiconductor device produced by an interconnection element with contact blade

ABSTRACT

An apparatus and method providing improved interconnection elements and tip structures for effecting pressure connections between terminals of electronic components is described. The tip structure of the present invention has a sharpened blade oriented on the upper surface of the tip structure such that the length of the blade is substantially parallel to the direction of horizontal movement of the tip structure as the tip structure deflects across the terminal of an electronic component. In this manner, the sharpened substantially parallel oriented blade slices cleanly through any non-conductive layer(s) on the surface of the terminal and provides a reliable electrical connection between the interconnection element and the terminal of the electrical component.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to the field ofelectrical interconnection (contact) elements, and, more particularly,to interconnection elements and tip structures suitable for effectingpressure connections between electronic components.

[0003] 2. Description of the Related Art

[0004] Generally, interconnections between electronic components can beclassified into the two broad categories of “relatively permanent” and“readily demountable”. An example of a relatively permanent connectionis a solder joint. Once two electronic components are soldered to oneanother, a process of unsoldering must be used to separate thecomponents. A wire bond, such as between a semiconductor die and theinner leads of a semiconductor package (or the inner ends of lead framefingers) is another example of a relatively permanent connection.

[0005] One example of a readily demountable connection is rigid pins ofone electronic component being received by resilient socket elements ofanother electronic component. The socket elements exert a contact force(pressure) on the pins in an amount sufficient to ensure a reliableelectrical connection therebetween. Another type of readily demountableconnection are interconnection elements (also referred to herein assprings, spring elements, spring contacts or spring contact elements)that are themselves resilient, springy, or mounted in and/or on a springmedium. An example of such a spring contact element is a needle of aprobe card component. Such spring contact elements are typicallyintended to effect temporary pressure connections between a component towhich they are mounted and terminals of another component, such as asemiconductor device under test.

[0006] Tip structures are often mounted (or affixed or coupled) to oneend of an interconnection element. Tip structures provide a desired tipshape to the interconnection elements and are particularly useful inproviding a small area contact with a controlled geometry that creates arepeatable high pressure. Tip structures become increasingly critical asthe interconnection elements themselves become smaller and smaller. Atip structure may also have topological features on its surface toassist in providing an electrical contact between the two electricalcomponents. For example, the purpose of the tip structure is typicallyto break through the nonconductive layer (often corrosion, oxidationproducts, or other types of contaminated films) on the terminals of theelectrical component under test. As a contact force is applied, theinterconnection element applies a pressure to the terminal of theelectronic component under test and causes the tip structure to deflectacross the terminal. This small horizontal movement of the tip structureacross the surface of the corresponding terminal allows the tipstructure to penetrate the nonconductive layer on the terminal, therebyestablishing a good electrical contact between the two electroniccomponents. For example, tip structure 10 mounted to interconnectionelement 12 (shown in FIGS. 1A and 1B) has a blade 14 that scrapes asidethe non-conductive layer in order to achieve an electrical contact.

[0007] There are a number of problems associated with achieving theabove-described electrical contact. First, as the terminal contact areasalso get smaller, the horizontal movement of the tip structure 10becomes an issue. Second, as the tip structure 10 is forced to deflectacross the terminal (see FIG. 1B), it may also be forced down and awayfrom the terminal causing the blade 14 of the tip structure 10 to rotateaway from the terminal as the tip structure 10 deflects across theterminal. The rotation of the blade 14 away from the terminal of theelectronic component under test reduces the chances of the tip structureachieving a dependable electrical contact with the terminal of theelectronic component. Further, as the tip structure scrapes across thenonconductive surface of the terminal in an effort to penetrate thenonconductive surface and establish a good electrical contact, strayparticles and buildup often occur along the blade 14 and upper surfaceof the tip structure 10. This buildup may contribute to high contactresistance between the tip structure and the terminal, which may causeinaccurate voltage levels during device testing due to the voltageproduced across the tip structure. The inaccurate voltage levels maycause a device to incorrectly fail, resulting in lower test yields whenthe contact is used in a device testing environment.

[0008] Thus, an interconnection element and tip structure that minimizebuildup along the blade of the tip structure and maximize contactpressure between the tip structure and the terminal of the electroniccomponent under test as the tip structure deflects across the surface ofthe terminal is desired.

SUMMARY OF THE INVENTION

[0009] An apparatus and method providing improved interconnectionelements and tip structures for effecting pressure connections betweenterminals of electronic components is described. The tip structure ofthe present invention has a sharpened blade oriented on the uppersurface of the tip structure such that the length of the blade issubstantially parallel to the direction of horizontal movement of thetip structure as the tip structure deflects across the terminal of anelectronic component. In this manner, the sharpened substantiallyparallel oriented blade slices cleanly through any nonconductivelayer(s) on the surface of the terminal and provides a reliableelectrical connection between the interconnection element and theterminal of the electrical component.

DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1A is a side view of an interconnection element and tipstructure known in the prior art.

[0011]FIG. 1B is a side view of an interconnection element and tipstructure, known in the prior art, under deflection.

[0012]FIG. 2A is a side view of an interconnection element and tipstructure of the present invention.

[0013]FIG. 2B is a pictorial illustration of one embodiment of a tipstructure of the present invention

[0014]FIG. 2C is a side view showing an interconnection element and tipstructure of the present invention under deflection.

[0015]FIG. 2D is a side view of an alternative embodiment of the presentinvention showing an interconnection element having a substantiallyparallel oriented blade at one end.

[0016]FIG. 3A is a cross-sectional view of an elongate interconnectionelement.

[0017]FIG. 3B is a cross-sectional view of an elongate interconnectionelement.

[0018]FIG. 3C is a cross-sectional view of an elongate interconnectionelement.

[0019]FIG. 4A is a pictorial illustration of a generalized embodiment ofthe invention, showing prefabricated contact tip structures and theinterconnection elements to which they will be joined.

[0020]FIG. 4B is a cross-sectional side view of the contact tipstructures of FIG. 4A joined by brazing to the interconnection elementsof FIG. 4A.

[0021]FIG. 4C is a cross-sectional side view of the contact tipstructures of FIG. 4A joined by brazing to the interconnection elementsof FIG. 1A, after the sacrificial substrate is removed.

[0022]FIGS. 5A-5C are cross-sectional views of steps in a process ofmanufacturing cantilevered tip structures on a sacrificial substrate forinterconnection elements, according to an embodiment of the invention.

[0023]FIG. 5D is a pictorial illustration of an embodiment of acantilevered tip structure formed on a sacrificial substrate, accordingto an invention.

[0024]FIG. 5E is a pictorial illustration of a second embodiment of acantilevered tip structure formed on a sacrificial substrate, accordingto an invention.

[0025]FIG. 5F is a side-view showing the cantilevered tip structure ofFIG. 5E mounted to a raised interconnection element on a surface of anelectronic component.

[0026]FIG. 5G is a front view of the cantilevered tip structure of FIG.5E mounted to a raised interconnection element on a surface of anelectronic component.

[0027]FIG. 5H is a cross-sectional view of a cantilevered tip structuremounted to a raised interconnection element illustrated in FIG. 5D.

[0028]FIG. 5I is a side cross-sectional view of another embodiment offabricating cantilevered tip structures, according to an alternateembodiment of the present invention.

[0029]FIG. 5J is a front cross-sectional view of the embodimentillustrated in FIG. 5I.

[0030]FIG. 5K is a side cross-sectional view of the cantilevered tipstructure illustrated in FIGS. 5I and 5J and mounted to an electroniccomponent, according to an alternate embodiment of the presentinvention.

[0031]FIG. 6A is a pictorial illustration of a tip structure of thepresent invention having a blade having pyramidal edges.

[0032]FIG. 6B is a pictorial illustration of a tip structure of thepresent invention having diamond shaped edges.

[0033]FIG. 7A is a top view of a tip structure of the present inventionhaving two blades.

[0034]FIG. 7B is a cross-sectional view of a tip structure of thepresent invention having two blades joined by a bridge.

[0035]FIG. 7C is a cross-sectional view of a tip structure of thepresent invention having two blades in a juxtaposed position.

[0036]FIG. 8A is a pictorial illustration of a tip structure of thepresent invention having a blade with a primary blade and a trailingblade.

[0037]FIG. 8B is a cross-sectional view of the tip structure of FIG. 8A.

[0038]FIG. 9A is a cross-sectional view of a tip structure andsubstantially parallel oriented blade of the present invention affixedto Cobra style probes.

[0039]FIG. 9B is a cross-sectional view of Cobra style probes having asubstantially parallel oriented blade at one end.

[0040]FIG. 10 is a pictorial illustration of a tip structure of thepresent invention having a stand-off blade.

DETAILED DESCRIPTION OF THE INVENTION

[0041] An apparatus and method that provides improved interconnectionelements and tip structures suitable for effecting pressure connectionsbetween terminals of electronic components is described. In thefollowing description, numerous specific details are set forth such asmaterial types, dimensions, processing steps, etc., in order to providea more thorough understanding of the present invention. However, it willbe obvious to one of skill in the art that the invention may bepracticed without these specific details. In other instances, well-knownelements and processing techniques have not been shown in particulardetail in order to avoid unnecessarily obscuring the present invention.Further, although the present invention is discussed with respect to useas a needle of a probe card component that provides an electricalconnection between the probe card and a terminal of an electricalcomponent under test, the present invention is not limited to use in aprobe card and may be used to provide electrical connections betweenother electrical components under other circumstances.

Overview of Present Invention

[0042] As previously discussed, there are a number of problemsassociated with using the interconnection elements and tip structurescurrently known in the art to achieve a good electrical contact betweentwo electronic components. The present invention addresses theseproblems by providing an interconnection element having a tip structurewith a sharpened blade oriented on the upper surface of the tipstructure such that the length of the blade runs substantially parallel(within approximately ±15° of parallel) to the direction of horizontalmovement of the tip structure as the tip structure deflects across theterminal of the electronic component under test. Through use of thepresent invention, a reliable electrical contact is established betweenthe electronic components. Once the tip structure contacts the terminalof the electronic component, the interconnection element forces the tipstructure to deflect across the surface of the terminal such that thetip structure blade slices through (penetrates) the non-conductivelayer(s) on the surface of the terminal. The electronic component may bean integrated circuit, an interconnect board, a semiconductor wafer, ora printed circuit board.

[0043]FIG. 2A is a side view of the present invention, showing a springcontact element 24 coupled to a substrate 26 at one end and having a tipstructure 20 coupled thereto at an opposite end. FIG. 2B is a pictorialillustration of the tip structure 20 of the present invention, having ablade 22 on the upper surface of the tip structure 20. In thisembodiment of the present invention, the blade 22 comprises a contactelement whose faces when extended form a line in space. When the tipstructure 20 is placed in contact with a terminal of an electroniccomponent (not shown) and a force is applied, the tip structure 20 willdeflect across the surface of the terminal. As the tip structure 20deflects across the terminal, the blade 22 of the tip structure 20 willpenetrate the non-conductive layer on the surface of the terminal. FIG.2C is a side view of the present invention. The dashed lines of FIG. 2Cshow the interconnection element 24 and tip structure 22 after thedeflection across the terminal. ΔX represents the amount of lateral (orhorizontal) deflection of the tip structure 20.

[0044] The blade 22 is oriented on the upper surface of the tipstructure 20 such that the length (L) of the blade is substantiallyparallel to the direction of horizontal movement (ΔX) of the tipstructure 20 as the tip structure 20 deflects across the surfaceterminal (see FIG. 2C). The orientation of the blade 22 substantiallyparallel to the direction of horizontal motion of the tip structure,allows the blade 22 to slice (or cut) through any non-conductivelayer(s) on the surface of the terminal.

[0045]FIG. 2D illustrates an alternative embodiment of the presentinvention, wherein the blade 26 is formed at the end of the springcontact element 28 itself, rather than being on a separate tipstructure. In this manner, a substantially parallel oriented blade 26may be formed without a transferred tip structure (such as tip structure20 in FIG. 2A). The blade 26 may be formed at the end of spring contact28 by several methods including but not limited to a plating ormachining process (such as the use of a stamp, swage, electropolish, orelectro-static discharge).

[0046] The orientation of the blade 22 on the upper surface of the tipstructure 20 (or the blade 26 formed at the end of spring element 28)substantially parallel to the direction of the horizontal motioncomponent of the tip structure 20 (hereinafter generally referred to asa parallel orientation) provides numerous advantages over prior art tipstructures. First, the parallel orientation of the sharpened edge alongthe length (L) of the blade 22 allows the blade 22 to cut cleanlythrough the non-conductive layer on the terminal and establish a goodelectrical connection with the terminal of the electric component beingtested. In contrast, the substantially perpendicular orientation of theblades of prior art tip structures (i.e. when the length of the blade isoriented on the upper surface of the tip structure substantiallyperpendicular to the direction of the horizontal motion component of thetip structure as the tip structure deflects across the surface of theterminal under test; for example, see blade 14 of FIGS. 1A and 1B)provides a scraping motion across the non-conductive layer. The priorart blade scrapes across the terminal surface much as a bulldozerscrapes aside a layer of dirt. The scraping motion of perpendicularoriented blades may damage the surface of the terminal, often causessignificant wear and tear on the blades resulting in a short life spanof the blades, and often results in a buildup of stray particles and thenon-conductive layers along the blade. In contrast, the paralleloriented blade 22 of the present invention circumvents each of theabove-described problems by following the direction of horizontal motioncomponent of the tip structure and cleanly slicing through thenon-conductive layer on the terminal. Further, there is minimal, if any,buildup along the surface of the blade 22 which results in a lowercontact resistance between the tip structure and the terminal andproduces more accurate voltage levels during testing.

[0047] The parallel orientation of the blade 22 also provides a morereliable electrical connection with the terminal of the electroniccomponent under test. As electronic component terminals become smaller,any movement by the blade becomes significant as the possibilityincreases that any movement will move the blade outside of the terminalsuch that the blade will be unable to establish an electrical contactwith the terminal. As shown in FIGS. 1B and 2C, the deflection of thetip structure (10, 20) across the terminal may depend on both theinterconnection element's material and shape. In one embodiment, the tipstructure deflects along a substantially rotational path having both alateral (or horizontal) and a vertical component to the motion resultingin both a lateral deflection and a vertical deflection as the tipstructure (10, 20) is pushed down and away from the terminal. It ispossible, that the perpendicularly oriented blade 14 will be pushedoutside of the terminal contact area as a result of the rotationalmovement of the tip structure 10. In contrast, as the tip structure 20deflects across the terminal, even if part of the blade 22 is movedoutside of the terminal contact area, the remaining length of the blade22 (the trailing end) continues to be within the terminal contact area.Likewise, even as the front end of blade 22 is forced to rotate down andaway from the terminal contact area, the trailing end of the blade 22will remain in contact with the terminal surface. In this manner, theparallel oriented blade 22 of the present inventor provides a morereliable electrical connection (or interface) with the terminal of theelectrical component under test.

Components of the Present Invention

[0048] The interconnection element and tip structure of the presentinvention may be manufactured by a variety of methods and from a varietyof materials. The following methods of manufacturing and types ofmaterials discussed are illustrative examples only and are not intendedto limit the invention in any manner. Other methods and materials knownin the art may also be followed and/or used.

[0049] Interconnection Element

[0050] Existing interconnection elements such as elongate and/orresilient interconnection elements may be used for the interconnectionelement of the present invention (element 24 of FIG. 2A). When usingresilient interconnection elements, a composite interconnection elementis one preferred form of contact structure (spring or spring-likeelement). FIGS. 3A-3C illustrate various shapes commonly used forcomposite interconnection elements. The tip structures of the presentinvention may be used on any spring-like elements including thosediscussed herein below and those shown in U.S. Pat. No. 5,476,211,issued on Dec. 19, 1995, assigned to the assignee of the presentinvention, and which is incorporated herein by reference.

[0051] In FIG. 3A, an electrical interconnection element 310 includes acore 312 of a “soft” material (e.g., a material having a yield strengthof less than 40,000 psi), and a shell (overcoat) 314 of a “hard”material (e.g., a material having a yield strength of greater than80,000 psi). The core 312 is an elongate element shaped (configured) asa substantially straight cantilever beam, and may be a wire having adiameter of 0.0005-0.0030 inches. The shell 314 is applied over thealready-shaped core 312 by any suitable process, such as by a suitableplating process (e.g., by electrochemical plating). It is generallypreferred that the thickness of the shell (whether a single layer or amulti-layer overcoat) be thicker than the diameter of the wire beingovercoated. By virtue of its “hardness”, and by controlling itsthickness (0.00025-0.02000 in.), the shell 314 imparts a desiredresiliency to the overall interconnection element 310. In this manner, aresilient interconnection between electronic components (not shown) canbe effected between the two ends 310 a and 310 b of the interconnectionelement 310.

[0052]FIG. 3A illustrates what is perhaps the simplest of spring shapesfor an interconnection element of the present invention, namely, astraight cantilever beam oriented at an angle to a force “F” applied atits tip 110 b. When such a contact force (pressure) is applied by aterminal of an electronic component to which the interconnection elementis making a pressure contact, the downward (as viewed) deflection of thetip will result in the tip moving across the terminal, in a “wiping”motion. Such a wiping contact ensures a reliable contact being madebetween the interconnection element and the contacted terminal of theelectronic component. The deflection (resiliency) of the interconnectionelement in general is determined in part by the overall shape of theinterconnection element, in part by the dominant (greater) yieldstrength of the overcoating material (versus that of the core), and inpart by the thickness of the overcoating material.

[0053] In FIG. 3B, an electrical interconnection element 320 similarlyincludes a soft core 322 (compare 312) and a hard shell 324 (compare314). In this example, the core 322 is shaped to have two bends, andthus may be considered to be S-shaped. As in the example of FIG. 3A, aresilient interconnection between electronic components (not shown) canbe effected between the two ends 320 a and 320 b of the interconnectionelement 320. In contacting a terminal of an electronic component, theinterconnection element 320 would be subjected to a contact force(pressure), as indicated by the arrow labeled “F”.

[0054] In FIG. 3C, an electrical interconnection element 330 similarlyincludes a soft core 332 (compare 312) and a hard shell 334 (compare314). In this example, the core 332 is shaped to have one bend, and maybe considered to be U-shaped. As in the example of FIG. 3A, a resilientinterconnection between electronic components (not shown) can beeffected between the two ends 330 a and 330 b of the interconnectionelement 330. In contacting a terminal of an electronic component, theinterconnection element 330 could be subjected to a contact force(pressure), as indicated by the arrow labeled “F”. Alternatively, theinterconnection element 330 could be employed to make contact at otherthan its end 330 b, as indicated by the arrow labeled “F”.

[0055] It should be understood that the soft core can readily be formedinto any springable shape-in other words, a shape that will cause aresulting interconnection element to deflect resiliently in response toa force applied at its tip. For example, the core could be formed into aconventional coil shape. However, a coil shape would not be preferred,due to the overall length of the interconnection element and inductance(and the like) associated therewith and the adverse effect of same oncircuitry operating at high frequencies (speeds). Likewise, the coreelement need not have a round cross-section, but may rather be a flattab (“ribbon”) having a generally rectangular cross-section andextending from a sheet. Other non-circular cross-sections, such asC-shaped, I-shaped, L-shaped and T-shaped cross-sections, may also beused for the interconnection element.

[0056] The material of the shell, or at least one layer of a multi-layershell (described hereinbelow) has a significantly higher yield strengththan the material of the core. Therefore, the shell overshadows the corein establishing the mechanical characteristics (e.g., resiliency) of theresulting interconnection structure. Ratios of shell:core yieldstrengths are preferably at least 2:1, and may be as high as 10:1. It isalso evident that the shell, or at least an outer layer of a multi-layershell should be electrically conductive, notably in cases where theshell covers the end of the core.

[0057] Suitable materials for the core (312, 322, 332) include, but arenot limited to: gold, aluminum, copper, and their alloys. Thesematerials are typically alloyed with small amounts of other metals toobtain desired physical properties, such as with beryllium, cadmium,silicon, magnesium, and the like. It is also possible to use silver,palladium, platinum; metals or alloys such as metals of the platinumgroup of elements. Solder constituted from lead, tin, indium, bismuth,cadmium, antimony, and their alloys can be used. Generally, a wire ofany material (e.g., gold) that is amenable to bonding (usingtemperature, pressure, and/or ultrasonic energy to effect the bonding)would be'suitable for practicing the invention. It is within the scopeof this invention that any material amenable to overcoating (e.g.,plating), including non-metallic material, can be used for the core.

[0058] Suitable materials for the shell (314, 324, 334) include, but arenot limited to: nickel, and its alloys; copper, cobalt, iron, and theiralloys; gold (especially hard gold) and silver, both of which exhibitexcellent current-carrying capabilities and good contact resistivitycharacteristics; elements of the platinum group; noble metals;semi-noble metals and their alloys, particularly elements of theplatinum group and their alloys; tungsten and molybdenum. In cases wherea solder-like finish is desired, tin, lead, bismuth, indium and theiralloys can also be used. The technique selected for applying thesecoating materials over the various core materials set forth above will,of course, vary from application-to-application. Electroplating andelectroless plating are generally preferred techniques.

[0059] Another type of electrical interconnection element that may beused with the present invention is a resilient interconnection elementthat is formed lithographically. An oriented blade of the invention maybe formed on a contact end of a lithographically formed resilientinterconnection element. In one example of the invention, an orientedblade may be formed on a sacrificial substrate and then transferred to acontact end of a lithographically formed resilient interconnectionelement.

[0060] The interconnection elements of the present invention (element 24of FIGS. 2A-2D) can generally be fabricated upon, or mounted to, anysuitable surface of any suitable substrate, including sacrificialsubstrates, then either removed therefrom or mounted to terminals ofelectronic components.

[0061] Coupling Interconnection Elements to Tip Structures

[0062]FIG. 4A illustrates a generalized embodiment 400 of the inventionwherein a plurality (four of many shown) of contact tip structures 402have been pre-fabricated upon a support (sacrificial) substrate 404, ina manner described hereinbelow. A corresponding plurality (four of manyshown) of interconnection elements 406 are shown in preparation forhaving their free ends 406 a joined to the contact tip structures 402(or vise-versa). The free ends 406 a of the elongate interconnectionelements 406 are distant (distal) from opposite ends (not shown) of theelongate interconnection elements 406 which typically would extend froma surface of an electronic component (not shown) such as a semiconductordevice, a multilayer substrate, a semiconductor package, etc.

[0063]FIG. 4B illustrates, in side view, a next step of joining thecontact tip structures 402 to the elongate interconnection elements 406by brazing. A resulting braze fillet 408 is illustrated. The contact tipstructures 402 are still resident on the sacrificial substrate 404 intheir prescribed spatial relationship with one another. FIG. 4B is alsoillustrative of the contact tip structures 402 being joined to theelongate interconnection elements with conductive adhesive (e.g.,silver-filled epoxy) or the like. An alternate method of joining thecontact tip structures 402 to the elongate interconnection elements 406is by overcoating at least the junction of the contact tip structures402 and adjacent end portions of the elongate interconnection elements406 with a metallic material such as nickel, by plating.

[0064]FIG. 4C illustrates, in a side view, a subsequent step, wherein,after joining the contact tip structures 402 to the elongateinterconnection elements 406, the support (sacrificial) substrate 404 isremoved. The resulting “tipped” interconnection element 406 (as usedherein, a “tipped” interconnection element is an interconnection elementwhich has had a separate contact tip structure joined thereto) is shownas having had a contact tip structure 402 brazed (408) thereto, in themanner described with respect to FIG. 4B.

[0065] In the embodiments described herein of forming free-standinginterconnection elements (either by themselves, or upon prefabricatedtip structures) on sacrificial substrates, the discussion has generallybeen directed to bonding an end of the interconnection element (or, inthe case of a composite interconnection element, bonding an elongatecore) to a sacrificial substrate. It is within the scope of thisinvention that instrumentalities (techniques) other than bonding can beemployed.

[0066] Tip Structures

[0067]FIGS. 5A-5H illustrate a technique 500 for fabricating tipstructures having a parallel oriented blade and mounting same tointerconnection elements which may serve as terminals of electroniccomponents, and FIGS. 5I-5K illustrate an alternate technique 550employing such tip structures. These techniques are particularly wellsuited to ultimately mounting freestanding interconnection elements toelectronic components such as semiconductor devices, space transformersubstrates of probe card assemblies, and the like.

[0068]FIG. 5A illustrates a sacrificial substrate 502, such as a waferof monocrystalline silicon, into a surface of which a plurality (one ofmany shown) trenches 504 are etched. A patterned masking layer, such asa photoresist (not shown), is first patterned on the substrate 50 todefine the length and width of the trench 504. Next, the trench 504 isformed in the substrate 504. In the preferred embodiment, a potassiumhydroxide (KOH) selective etch is performed between the 111 and 001crystal orientation.

[0069] Note that methods other than a KOH selective etch may be used toform the trench 504 used to form the blades of the present invention.For example, the trenches may also be formed with a reactive ion etch(RIE). Further, non-lithographic methods may also be employed, includingbut not limited to polishing (both electro-polishing and mechanicalpolishing) stamping, or abrading the tip structures. Combinations ofstraight walled and trenched structures may also be produced bycombining different etching techniques. Such combinations may bedesirable to create stand-off structures such as the one illustrated inFIG. 10. As with the tip structures discussed herein above, tipstructure 980 is comprised of a tip base 982 and tip blade 984. Tipstructure 980, however, also includes a straight-walled section 986 thatprovides the stand-off distance (D) for the tip structure 980.

[0070] The preferred embodiment comprises a tip structure with a bladeon the upper surface, wherein the blade has a sharpened edge along thelength of the blade and a triangular cross-section. However, thetrenches 504 are merely illustrative of any surface texture ‘template’for the tip structures which will be fabricated on the sacrificialsubstrate 502. The layout (spacing and arrangement) of the trenches 504can be derived from (replicate) the bond pad layout of a semiconductordie (not shown) which is ultimately (in use) intended to be contacted(e.g., probed) by free-standing interconnection elements to which thetip structures 504 are ultimately attached. For example, the trenches504 can be arranged in a row, single file, down the center of thesacrificial substrate. Many memory chips, for example, are fabricatedwith a central row of bond pads.

[0071]FIG. 5B illustrates that a hard “field” layer 506 has beendeposited upon the surface of the sacrificial substrate 502, includinginto the trenches 504. The field layer 506 will serve as a releaselayer. One possible release layer is comprised of aluminum having anapproximate thickness of 5000 Å. Another layer 508 can optionally bedeposited over the field layer 506, if the field layer is of a materialwhich is not amenable to plating. Typically, layer 508 is comprised ofcopper having an approximate thickness of 5000 Å. (If the layer 506 isdifficult to remove, it may be applied by selective deposition (e.g.,patterning through a mask), to avoid such removal.) After the contactstructures are fabricated within the trench (see below), the sacrificialsubstrate 502 may be removed by any suitable process, such as byselective chemical etching.

[0072] Note also, however, that in addition to a chemical etchant,appropriate metallurgy can be used in conjunction with heat to releasethe sacrificial substrate 502. For example, in one embodiment of thepresent invention, layer 506 comprises a non-wettable material such astungsten (or titanium tungsten) deposited on the substrate 502 by meanssuch as sputtering. Next, the thin layer 508 is deposited comprising anon-wetting material such as plateable lead (or indium) onto thetungsten layer 506. Then, after the contact tip structures arefabricated within the trench (see below), a reflow technique (usingheat) may be used to mount the contact tip structures ontointerconnection elements. During reflow, the lead (material 508) willmelt and ball up, since tungsten (material 506) is not wettable withrespect to lead. This causes the contact tip structures to be releasedfrom the sacrificial substrate 502. Optionally, a second layer (notshown) of non-wettable material (e.g., tungsten) can be applied overlayer 508, and will become part of the resulting contact tip structureunless removed (e.g., by etching). Further, another layer of materialwhich will ball up when heated (e.g., lead, indium) can be applied overthe second layer of non-wettable material (e.g., tungsten). Any residuallead on the surface of the resulting contact tip structure is readilyremoved, or may be left in place. Alternatively, a layer of a “barrier”material can be deposited between the second layer of material whichwill ball up and the first layer of the fabricated contact tipstructure. The “barrier” material may be tungsten, silicon nitride,molybdenum, or the like.

[0073] Once layers 506 and 508 are deposited, a masking material 510(illustrated in FIG. 5C), such as photoresist, is applied to define aplurality of openings for the fabrication of tip structures. Theopenings in the masking layer 510 define a region around the trenches504. First, a contact metal 512 is deposited, typically having a minimumthickness of approximately 0.5 mil. This contact metal may be depositedby sputtering, CVD, PVD, or plating. In one embodiment of the presentinvention, the contact metal 512 is comprised of Palladium-Cobalt. Othermaterials may also be used for contact metal 512, including but notlimited to, palladium, rhodium, tungsten-silicide, tungsten, or diamond.Next, layer 514 comprised of a spring alloy material (such as nickel andits alloys) is optionally deposited (such as by plating) to crease thebulk of the tip structure. Layer 514 typically has an approximatethickness of 0-2 mils. Over layer 514, a layer 516 is depositedcomprising a material amenable to brazing or soldering, in the eventthat the spring alloy is not easy to bond, solder or braze to. Thespring alloy layer 514 is deposited by any suitable means such asplating, sputtering, or CVD. Finally, a Au-Braze joining layer 516 isdeposited. The Au-Braze layer is specific to an AuSn braze attach.

[0074] Next, as illustrated by FIGS. 5D and 5E, the masking material 510is stripped (removed), along with that portion of the layers (506 and508) which underlies the masking material 510, resulting in a plurality(one of many shown) of tip structures (520 and 520 a) having beenfabricated upon the sacrificial substrate 502. FIG. 5D shows a firstembodiment of a tip structure 520 of the present invention having ablade 522 that extends the entire length of the foot of the tipstructure 520. FIG. 5E shows a second embodiment of a tip structure 520a of the present invention having a blade 522 a that extends along apotion of the foot of tip structure 520 a. Tip structure 520 a also hasa back portion 521 wherein the blade 522 a does not extend through thefoot of the tip structure 520 a. The two alternate embodiments of tipstructures 520 and 520 a serve the same function in providing anelectrical contact with the terminal of an electronic component undertest, but provide different surfaces for coupling the tip structure 520and 520 a to an interconnection element.

[0075]FIGS. 5F and 5G illustrate the mounting of the tip structures 520a shown in FIG. 5E to raised interconnection elements 530 extending(e.g., free-standing) from corresponding terminals (one of many shown)532 of an electronic component 534. FIG. 5F shows a side view of mountedtip structures 520 a and FIG. 5G shows a front view of mountedcantilever tip structures 520. The interconnection element is coupled tothe foot of the tip structure 520 a along the back portion 521 of thetip structure 520 a where the blade 522 a does not extend and thesurface of the foot of the tip structure 520 a is flat. Thepre-fabricated tip structures 520 a is mounted to the tips (top, asshown) of the interconnection elements 530, in any suitable manner suchas brazing or soldering.

[0076]FIG. 5H illustrates the mounting of the tip structure 520 shown inFIG. 5D to raised interconnection elements 530 extending (e.g.,free-standing) from corresponding terminals (one of many shown) 532 ofan electronic component 534. In this embodiment of the presentinvention, the solder paste or brazing material used to mount the tipstructure 520 to the interconnection element 530 is positioned withinthe divot 523. The end result is a mounted tip structure similar to thatillustrated in FIGS. 5F and 5G, with the interconnection element affixedto the divot 523 rather than a flat back section (see 521 of FIG. 5F).Using the divot formed when fabricating the blade 522 aids inpositioning the solder paste or brazing material and provides a morereliable method of forming the mechanical connection between theinterconnection element 530 and the foot of the tip structure 520.

[0077] The raised interconnection elements 530 can be any free-standinginterconnection elements including, but not limited to, compositeinterconnection elements, and specifically including contact bumps ofprobe membranes (in which case the electronic component 534 would be aprobe membrane) and tungsten needles of conventional probe cards. Theinterconnection element may be formed lithographically or through abonding and plating operation as in U.S. Pat. No. 5,476,211. The raisedinterconnection elements, although typically resilient and providing aspring-like motion, may also be rigid posts. Note that the shape of theresilient element to which the tip structures are attached will affectthe wipe characteristic (i.e., the horizontal movement of the tipstructure across the surface of the terminal contact of the device undertest) in probing. External forces, such as machine-controlled movement,may also affect the wipe characteristic. Thus, the interconnectionelements may be designed to optimize a desired contact behavior.

[0078] FIGS. 5I-K illustrate another technique 550 of employing tipstructures, wherein the tip structures are provided with their ownraised contacts (interconnection elements) prior to being mounted toterminals of an electronic component. This technique commences with thesame steps of forming trenches 504 in a surface of a sacrificialsubstrate 502, applying a field layer 506, applying an optional brazinglayer 508, and applying a masking material 510 with openings definingthe locations and shapes of the resulting tip structures. Compare FIGS.5A-5C above.

[0079] In a next step, as illustrated by FIGS. 5I-J (FIG. 51 is a sideview and FIG. 5J is a front view), a freestanding interconnectionelement 552 is mounted to the back end portion of the tip structure 530.Then, with use of a masking layer 510, a layer of hard (springy)material 554 is deposited over the tip structure (and, optionally,another layer such as 516 which is brazeable, see above). The maskinglayer 510 is stripped, and the tip structure 570 can be mounted toterminals 582 of an electronic component 584, by soldering or brazingthe tips of the free-standing interconnection elements 552 to terminals582, as indicated by the solder fillet 586. Note that in the alternatemounting technique shown in FIGS. 5I-K, the coupling step (typicallysoldering or brazing) occurs when coupling the interconnection elementto an electronic component, wherein with the first mounting techniquedescribed in FIGS. 5A-H, the coupling step joins the tip structure tothe interconnection element. In other words, when contrasting the twomounting techniques, the coupling step of soldering or brazing isperformed on opposite ends of the interconnection element.

[0080] In these examples, the interconnection elements 520 and 570 areillustrated as being composite interconnection elements having springshapes, but it should clearly be understood that the invention isexpressly not limited thereto. In either case (500, 550) the result isthat an electronic component (534, 584) is provided with a plurality offree-standing interconnection elements (530, 552) extending fromterminals thereof, the tips (free ends) of the free-standinginterconnection elements 520 being provided with tip structures having asurface texture which is imparted (defined) during the process offabricating the tip structures on the sacrificial substrate 502.

[0081] It is evident from the preceding descriptions that theinterconnection elements alone (530, 552 (i.e., 552 overcoated by 554))need not be resilient. Resilience may be provided by the ability of thecantilever tip structures (520, 570) to deflect in response to making apressure connection with another electronic component (not shown)because the tip structures 504 are disposed along a cantilever beam.Preferably, the freestanding interconnection elements 520 are muchstiffer than the cantilever beams, so that the contact force resultingfrom a pressure connection can be well defined and controlled.

[0082] In any cantilever beam arrangement, it is preferred that one endof the cantilever be “fixed” and the other end “movable”. The cantileverbeam may serve as a foot for a tip structure or a foot of aprefabricated tip structure may be mounted onto a separately fabricatedbeam. In this manner, bending moments are readily calculated. Hence, itis evident that the elongate interconnection elements (530, 552) arepreferably as rigid as possible. (In the case where the interconnectionelements (530) are contact bumps on a membrane probe, resiliency isprovided by the membrane (534), itself.) However, it is not entirely inapposite that the elongate interconnection elements are implemented ascomposite interconnection elements, such as the compositeinterconnection elements discussed above, which will contribute to theoverall deflection of the tip structures in response to pressureconnections being made to (by) the tip structures.

ALTERNATIVE EMBODIMENTS UTILIZING THE PRESENT INVENTION

[0083] The cross-section of the tip section blade as discussed above istriangular. However, other cross-sections may also be used. For example,a truncated pyramid could easily be fabricated in a similar manner tothat described above. Note also, that a tip structure initiallyfabricated to have a sharp edge blade along the length of the tipstructure will often become flat-topped as it wears with use. This“flat-top” results in a cross-section very similar to a truncatedpyramid. A tip structure having a truncated pyramid cross-section stillmaintains the benefits of a parallel oriented blade outlined above.

[0084] Different embodiments of the parallel oriented blade of thepresent invention may have different front and back edges. For example,in some instances, the blades may have rectilinear edges (i.e. edgesthat are perpendicular to the tip structure) such as the blade 522 beingfabricated in FIG. 5D. FIG. 6A shows an alternate blade 600 withpyramidal front and back edges 602. On blade 600, the front and backedges 602 are at an angle larger than 900 from the foot of the tipstructure 604. A second alternate blade 610 having a diamond shape isillustrated in FIG. 6B. Blade 610 is formed by performing a KOH etch at450 relative to the primary axis of the lattice and then defining thephoto resist etch widow as having 6 sides (or as having a hexagonalshape). This results in a tip structure 614 having a diamond shape blade610 on its top surface.

[0085] There are many other alternative embodiments that benefit fromthe numerous advantages provided by the parallel oriented blade of thepresent invention. For example, more than one blade 700 may befabricated on a tip structure, as shown in a top view of tip structure702 in FIG. 7A. This embodiment would be particularly useful for probingcontrolled collapse chip connection (C4) solder balls or other sphericalstructures.

[0086] Another variation of the embodiment of the present inventionhaving two or more blades fabricated on a single foot is shown in FIG.7B. FIG. 7B is a front view of a tip structure 714 showing two blades710 joined by a bridge 712, and having an included stand-off 716.Additionally, with multiple blades formed on a tip structure, thepre-determined pitch between blades would be particularly useful withspherical probing having a fine pitch.

[0087]FIG. 7C is a side view of a third embodiment of the presentinvention having two or more blades fabricated on a single foot. On tipstructure 724, two blades 720 are placed in a juxtaposed position andshare a common trench 722 having a stand-off height of H. The juxtaposedblades 720 are particularly useful in situations for fine pitchapplications with contact surfaces in close proximity.

[0088] Another embodiment utilizing the present invention is amulti-height blade such as blade 800 shown in FIGS. 8A and 8B. Blade 800has a primary blade 802 toward the front edge of the tip structure 806,and a trailing blade 804 toward the back of the tip structure 806. Theblade 800 may be formed using a masking process wherein the masksurrounding the shorter, trailing blade 804 provides a smaller hole suchthat the trench etch by the KOH etch is shallow, and the masksurrounding the taller, front blade provides a larger hole such that thetrench etch by the KOH etch is deeper and the blade 806 will be taller.

[0089] The present invention may also be used with the conventionalCobra style probes, a partial view of which is shown in FIG. 9A. Cobrastyle probes utilize prebended contact wires 906 positioned verticallyand maintained by two guide plates 908 and 910. The perforated guideplates 908 and 910 hold and direct the wires 906. The Cobra style probessuffer from the restriction that the contact geometry is determined bythe use of round wire, and that the contact metallurgy is that of thespring itself. Use of transferred tip structures of the presentinvention yield a controlled geometry, decoupling contact, and springmetallurgy. Thus, it is advantageous to affix the tip structures 900 tothe ends of the contact wires 906. The guide plates 908 and 910 willthen direct both the contact wires 906 and the tip structures 900 withparallel oriented blades 902 of the present invention affixed theretoacross the terminals of an electronic component under test. In thismanner, various embodiments of the present invention may be used inconjunction with Cobra style probes to provide a more reliableelectrical connection between the Cobra style probes 906 and theterminal of the electrical component under test.

[0090] Alternatively, FIG. 9B illustrates another embodiment of thepresent invention having parallel oriented blades 912 at the ends ofcontact wires 906. In the same manner as described previously withrespect to FIG. 2D, the blades 912 may be formed at the end of thecontact wires 906 by, for example, a plating or machining process. Thus,the contact wires 906 have a blade tip or “chiseled head” 912 withoutthe use of a transferred tip structure. Note also, that each of thealternative embodiments discussed above and below in reference to FIGS.6A, 6B, 7A, 7B, 7C, 8A, and 8B may be modified for use with a blade(such as blade 912) formed at the end of an interconnection element thatdoes not use a transferred tip structure.

[0091] Although the preferred embodiment of the present invention hasthe sharpened blade of the tip structure oriented such that the lengthof the blade is substantially parallel to the horizontal movement of thetip structure as the tip structure deflects across the surface of theterminal of the electronic component under test, an alternativeembodiment orients the blade such that the length of the blade ispositioned at a slight angle off parallel. For example, one embodimentmay encompass a blade oriented at an angle such that the length of theblade is within approximately 45° of the axis parallel to the horizontalmovement of the tip structure as the tip structure deflects across thesurface of the terminal of the electronic component under test. Ideally,the blade(s) will be at an approximate ±30° angle to the paralleloriented axis. Thus, this embodiment is able to provide a modifiedscraping motion across the surface of the terminal under test whileminimizing the amount of buildup accumulating along the blade 800.

[0092] Equipment for probing often includes an aligning feature. Suchaligning equipment may comprise optical sensors using light beams todetect the reflection off the tip structures. Each of the abovedescribed embodiments may be further improved to include a blade designhaving a better reflection. More reflective blades and/or tip structureswould provide a method for automatic recognition for classification andalignment purposes (e.g., alignment operations performed automaticallyin a wafer prober). The reflective ability of a blade is dependent on aflat upper surface at the tip of the blade (i.e. a blade having across-section of a truncated pyramid). The amount of reflection iscontrolled by controlling the length of time the initial trench (i.e.the trench used to form the blade) is etched, such that the trench doesnot come to a sharp point at its tip. Another method of controlling theamount of reflection per blade involves inserting reflow glass in thebottom of the trench before depositing the aluminum and copper layers.The glass at the tip of the trench softens the edge (or tip) of theblade and results in a blade having a cross-section similar to atruncated pyramid. Alternatively, the blade tips could be made having asharpened edge in the manner described above with the sharpened edgethen sanded (or grinded) down such that the blade has a flat top edgethat is reflective. Both of these alternative methods of creating areflective blade are easy to incorporate into the manufacture process

[0093] Thus, an apparatus and method providing improved interconnectionelements and tip structures for effecting pressure connections betweenterminals of electronic components is described. The sharpened bladeoriented on the upper surface of the tip structure such that the lengthof the blade is substantially parallel to the direction of horizontalmovement of the tip structure as the tip structure deflects across theterminal of an electronic component under test provides numerousadvantages over the prior art. The substantially parallel oriented bladeallows the tip structure of the present invention to slice cleanlythrough any non-conductive layers on the surface of the terminal andeffect a reliable electrical contact without damaging the surface of theterminal or acquiring particle buildup along the surface of the blade.Further, the parallel orientation of the blade of the present inventionmaximizes contact between the tip structure and the terminal such thatelectrical contact is not lost as the tip structure deflects across theterminal, even with terminals having smaller contact areas.

We claim:
 1. An electrical apparatus, comprising: at least one blade onan end of an interconnection element, said blade having a given lengthand oriented on the interconnection element such that said length runssubstantially parallel to a horizontal motion of said blade relative toan electrical terminal.
 2. The electrical apparatus of claim 1 whereinthe horizontal motion of said blade occurs when said blade makes anelectrical contact with the electrical terminal.
 3. The electricalapparatus of claim 2 wherein said blade has a truncated pyramidcross-sectional structure.
 4. The electrical apparatus of claim 2wherein said blade has a sharpened edge along said length of said blade.5. The electrical apparatus of claim 4 wherein said blade has across-sectional structure with a front edge at a first end of saidlength of said blade and a back edge at a second end of said length ofsaid blade.
 6. The electrical apparatus of claim 5 wherein said frontand back edges are rectilinear.
 7. The electrical apparatus of claim 5wherein said front and back edges are pyramidal.
 8. The electricalapparatus of claim 5 wherein said front and back edges have two sidessuch that said blade has a hexagonal shape.
 9. A tip structure,comprising: a foot having an upper and a lower surface; and, at leastone blade on said upper surface of said foot, said blade having a givenlength and oriented on said foot such that said length runssubstantially parallel to a horizontal motion of said foot.
 10. The tipstructure of claim 9 wherein the horizontal motion of said foot occurswhen said tip structure makes an electrical contact with an electricalterminal.
 11. The tip structure of claim 9 further comprising aresilient contact element coupled to said lower surface of said foot.12. The tip structure of claim 9 wherein said blade has a sharpened edgealong said length of said blade.
 13. The tip structure of claim 12wherein said blade has a primary edge at a front end of said blade and atrailing edge at a back end of said blade.
 14. The tip structure ofclaim 12 having a first and a second blade on said upper surface of saidfoot.
 15. The tip structure of claim 14 wherein said first and secondblades are joined by a bridge.
 16. The tip structure of claim 14 whereinsaid first and second blades are in a juxtaposed position.
 17. The tipstructure of claim 12 wherein said blade has a triangularcross-sectional structure with a front edge at a first end of saidlength of said blade and a back edge at a second end of said length ofsaid blade.
 18. The tip structure of claim 17 wherein said front andback edges are rectilinear.
 19. The tip structure of claim 17 whereinsaid front and back edges are pyramidal.
 20. The tip structure of claim17 wherein said front and back edges have two sides such that said bladehas a hexagonal shape.
 21. A tip structure, comprising: a foot having anupper and a lower surface; and, at least one blade on said upper surfaceof said foot, said blade having a given length and oriented on said footsuch that said length is within approximately ±45° of an axis parallelto a horizontal motion of said foot.
 22. The tip structure of claim 21wherein said blade has a sharpened edge along said length of said blade.23. The tip structure of claim 22 having a first and a second blade onsaid upper surface of said foot.
 24. The tip structure of claim 23wherein said first and second blades are joined by a bridge.
 25. The tipstructure of claim 23 wherein said first and second blades are in ajuxtaposed position.
 26. The tip structure of claim 22 wherein saidblade has a triangular cross-sectional structure with a front edge at afirst end of said length of said blade and a back edge at a second endof said length of said blade.
 27. The tip structure of claim 26 whereinsaid-front and back edges are rectilinear.
 28. The tip structure ofclaim 26 wherein said front and back edges are pyramidal.
 29. The tipstructure of claim 26 wherein said front and back edges have two sidessuch that said blade has a hexagonal shape.
 30. An electrical contactstructure comprising: a plurality of interconnection elements disposedin relationship with one another; a plurality of tip structures affixedto respective ones of said interconnection elements, each of said tipstructures further comprising: at least one blade on a contact point ofa respective one of said interconnection elements, said blade having agiven length and oriented on the respective one of said interconnectionelements such that said length runs substantially parallel to ahorizontal motion of the respective one of said interconnection elementswhen the respective one of said interconnection elements makes anelectrical contact.
 31. The electrical contact structure of claim 30wherein the horizontal motion of said foot occurs when said tipstructure makes electrical contact with en electrical surface.
 32. Theelectrical contact structure of claim 31 wherein said blade has asharpened edge along said length of said blade.
 33. The electricalcontact structure of claim 32 wherein said blade has a triangularcross-sectional structure with a front edge at a first end of saidlength of said blade and a back edge at a second end of said length ofsaid blade.
 34. The electrical contact structure of claim 33 whereinsaid front and back edges are rectilinear.
 35. The electrical contactstructure of claim 33 wherein said front and back edges are pyramidal.36. The electrical contact structure of claim 33 wherein said front andback edges have two sides such that said blade has a hexagonal shape.37. A method of making an electrical contact structure, comprising thesteps of: forming a trench in a sacrificial substrate; depositing atleast one layer of at least one conductive material in said trench toform a blade having a given length, an upper surface, and a lowersurface; and, coupling an interconnection element to said lower surfaceof said blade, wherein said blade is oriented such that said length ofsaid blade runs substantially parallel to a horizontal motion of saidblade.
 38. The method of claim 37 further comprising the step ofreleasing said blade from said sacrificial substrate.
 39. The method ofclaim 38 wherein said step of releasing said blade from said sacrificialsubstrate further comprises releasing said blade from said sacrificialsubstrate by a process selected from the group consisting of heat andchemical etching.
 40. The method of claim 37 wherein said step offorming a trench further comprises etching a trench in a substrate witha potassium hydroxide selective etch.
 41. The method of claim 40 whereinsaid step of etching a trench further comprises etching a trench in asubstrate with a potassium hydroxide etch between the 111 and 001crystal orientation.
 42. The method of claim 37 wherein said step offorming a trench further comprises forming a trench in a substrate,wherein said trench has a triangular cross-section.
 43. The method ofclaim 37 wherein said step of forming a trench further comprises forminga trench in a substrate, wherein said trench has a truncated pyramidcross-section.
 44. The method of claim 37 wherein said step of couplingsaid interconnection element to said lower surface of said blade furthercomprises soldering said interconnection element to said lower surfaceof said blade.
 45. The method of claim 37 wherein said step of couplingsaid interconnection element to said lower surface of said blade furthercomprises brazing said interconnection element to said lower surface ofsaid blade.